Direct transition between a singlet Mott insulator and a superconductor

We argue that a normal Fermi liquid and a singlet, spin-gapped Mott insulator cannot be continuously connected, and that some intermediate phase must intrude between them. By explicitly working out a case study where the singlet insulator is stabilized by orbital degeneracy and an inverted Hund's rule coupling, mimicking a Jahn-Teller effect, we find that the intermediate phase is a superconductor.     

A characterization of varieties whose universal cover is the polydisk or a tube domain

In this article we give necessary and sufficient conditions, in terms of certain tensors called semispecial tensors, respectively slope zero tensors, in order that the universal covering of a complex projective manifold be a symmetric domain of tube type. As an application, we give precisions of a result of Kazhdan showing that a Galois conjugate of such a manifold has the same universal covering.     

Level Algebras of Type 2

In this article, we study standard graded Artinian level algebras, in particular those whose socle-vector has type 2. Our main results are: the characterization of the level h-vectors of the form (1, r,…,r, 2) for r ≤ 4; the characterization of the minimal free resolutions associated to each of the h-vectors above when r = 3; a sharp upper-bound (under certain mild hypotheses) for the level h-vectors (1,r,…,a, 2) of arbitrary codimension r and type 2, which depends on the next to last entry a.     

Pure O-Sequences and Matroid h-Vectors

We study Stanley’s long-standing conjecture that the h-vectors of matroid simplicial complexes are pure O-sequences. Our method consists of a new and more abstract approach, which shifts the focus from working on constructing suitable artinian level monomial ideals, as often done in the past, to the study of properties of pure O-sequences. We propose a conjecture on pure O-sequences and settle it in small socle degrees. This allows us to prove Stanley’s conjecture for all matroids of rank 3. At the end of the paper, using our method, we discuss a first possible approach to Stanley’s conjecture in full generality. Our technical work on pure O-sequences also uses very recent results of the third author and collaborators.     

Strong monogamy of bipartite and genuine multipartite entanglement: the Gaussian case

We demonstrate the existence of general constraints on distributed quantum correlations, which impose a trade-off on bipartite and multipartite entanglement at once. For all N-mode Gaussian states under permutation invariance, we establish exactly a monogamy inequality, stronger than the traditional one, that by recursion defines a proper measure of genuine N-partite entanglement. Strong monogamy holds as well for subsystems of arbitrary size, and the emerging multipartite entanglement measure is found to be scale invariant. We unveil its operational connection with the optimal fidelity of continuous variable teleportation networks.     

Monogamy inequality for distributed gaussian entanglement

We show that for all n-mode Gaussian states of continuous variable systems, the entanglement shared among n parties exhibits the fundamental monogamy property. The monogamy inequality is proven by introducing the Gaussian tangle, an entanglement monotone under Gaussian local operations and classical communication, which is defined in terms of the squared negativity in complete analogy with the case of n-qubit systems. Our results elucidate the structure of quantum correlations in many-body harmonic lattice systems.     

Cathodic electrografting of versatile ligands on Si(100) as a low-impact approach for establishing a Si--C bond: a surface-coordination study of substituted 2,2'-bipyridines with CuI ions

Three distinct wet chemistry recipes were applied to hydrogen-terminated n- and p-Si(100) surfaces in a comparative study of the covalent grafting of two differently substituted 2,2'-bipyridines. The applied reactions require the use of heat, or visible light under a controlled atmosphere, or a suitable potential in an electrochemical cell. In this last case, hydrogen-terminated silicon is the working electrode in a cathodic electrografting (CEG) reaction, in which it is kept under reduction conditions. The resulting Si--C bound hybrids were characterized by a combination of AFM, dynamic contact-angle, and XPS analysis, with the help of theoretical calculations. The three distinct approaches were found to be suitable for obtaining ligand-functionalized Si surfaces. CEG resulted in the most satisfactory anchoring procedure, because of its better correlation between high coverage and preservation of the Si surface from both oxidation and contamination. The corresponding Si-bipyridine hybrid was reacted in a solution of CH3CN containing CuI ions coordinatively bound to the anchored ligands, as evidenced from the XPS binding-energy shift of the N atom donor functions. The reaction gave a 1:2 Cu-bipyridine surface complex, in which two ligands couple to a single CuI ion. The surface complex was characterized by the Cu Auger parameter and Cu/N XPS atomic-ratio values coincident with those for pure, unsupported CuI complex with the same 2,2'-bipyridine. Further support for such a specific metal-ligand interaction at the functionalized Si surface came from the distinct values of Cu2p binding energy and the Cu Auger parameter, which were obtained for the species resulting from CuI ion uptake on hydrogen-terminated Si(100).     

Effective method to compute vibrationally resolved optical spectra of large molecules at finite temperature in the gas phase and in solution

The authors present a new method for the computation of vibrationally resolved optical spectra of large molecules, including the Duschinsky rotation of the normal modes and the effect of thermal excitation. The method automatically selects the relevant vibronic contributions to the spectrum, independently of their frequency, and it is able to provide fully converged spectra with moderate computational times, both in vacuo and in solution. By describing the electronic states in the frame of the density functional theory and its time-dependent extension, they computed the room temperature absorption spectra of coumarin C153 and trans-stilbene in cyclohexane and the phosphorescence spectrum of porphyrazine in gas phase, showing that the method is fast and efficient. The comparison with experiment for trans-stilbene and coumarin C153 is very satisfactory, confirming the progress made toward a reliable method for the computation and interpretation for the optical spectra of large molecules.     

Novel virtual screening protocol based on the combined use of molecular modeling and electron-ion interaction potential techniques to design HIV-1 integrase inhibitors

HIV-1 integrase (IN) is an essential enzyme for viral replication and represents an intriguing target for the development of new drugs. Although a large number of compounds have been reported to inhibit IN in biochemical assays, no drug active against this enzyme has been approved by the FDA so far. In this study, we report, for the first time, the use of the electron-ion interaction potential (EIIP) technique in combination with molecular modeling approaches for the identification of new IN inhibitors. An innovative virtual screening approach, based on the determination of both short- and long-range interactions between interacting molecules, was employed with the aim of identifying molecules able to inhibit the binding of IN to viral DNA. Moreover, results from a database screening on the commercial Asinex Gold Collection led to the selection of several compounds. One of them showed a significant inhibitory potency toward IN in the overall integration assay. Biological investigations also showed, in agreement with modeling studies, that these compounds prevent recognition of DNA by IN in a fluorescence fluctuation assay, probably by interacting with the DNA binding domain of IN.     

Anti-angiogenic activity evaluation of secondary metabolites from Calycolpus moritzianus leaves

Angiogenesis is a crucial step in many pathological conditions like cancer, inflammation and metastasis formation; on these basis the search for antiangiogenic agents has widened. In order to identify new compounds able to interfere in the Vascular Endothelial Growth Factor Receptor-1 (VEGFR-1, also known as Flt-1) recognition by VEGFs family members, we screened Calycolpus moritzianus (O. Berg) Burret leaves extracts by a competitive ELISA-based assay. MeOH and CHCl3 extracts and several their fractions demonstrated to be able to prevent VEGF or PlGF interaction with Flt-1, with an inhibition about 50% at concentration of 100 microg/mL. Phytochemical and pharmacological investigation of the active fractions led to the isolation of flavonoids, and terpenes.